Sharyn, can you call the company and see if they'll send you a free sample?
I contacted Quilter's Dream on FB and asked if they had a sample book I could purchase, I was interested in the different weights of their batting. They sent me a sample book for free.
Just Janet - would you consider quilting your GFG to something like fleece and not using a backing at all? Or maybe flannel (although I find some flannel to be on the heavy side). Maybe audition the top with fleece and see if it's too heavy before quilting it.